Thermoplastic roofing membranes for fully-adhered roofing systems

ABSTRACT

A roof system comprising a substrate and thermoplastic membrane adhered to the substrate, where the thermoplastic membrane is characterized, prior to being adhered to the substrate, by a stiffness represented by a flexural modulus of less than 90 MPa, or by a Taber stiffness of less than 15, or by a Shore D hardness of less than 40, or by a combination of a flexural modulus of less than 90 MPa, a Taber stiffness of less than 15, and a Shore D hardness of less than 40.

This application is a continuation application of U.S. application Ser.No. 15/306,537 filed on Oct. 25, 2016, which is a U.S. National-StageApplication of PCT/US2015/027698 filed on Apr. 27, 2015, and whichclaims the benefit of U.S. Provisional Application Ser. No. 61/984,306filed on Apr. 25, 2014, which are incorporated herein by reference.

FIELD OF THE INVENTION

Embodiments of the present invention provide thermoplastic roofingmembranes that are useful for fully-adhered roofing systems andfully-adhered roofing systems prepared therewith; the overall membranesare characterized by an advantageously low stiffness.

BACKGROUND OF THE INVENTION

Thermoplastic roofing membranes, especially those membranes engineeredto cover flat or low-sloped roofs, are known in the art. In fact, manyof these membranes are engineered to meet the industry standards definedin ASTM D 790. Among the performance requirements provided in thisindustry standard, thermoplastic roofing membranes must meet thresholdrequirements for tensile strength and tear strength. Tensile strength isan indicator of seam strength, and the seam strength must withstand winduplift forces. Tear strength is primarily important from the standpointof fastener pull through. That is, where the membrane is mechanicallyattached to the roof surface, the membrane must be able to withstandthreshold wind uplift forces without tear at the location of thefastener.

Many commercially-available thermoplastic roofing membranes includefabric-reinforced thermoplastic sheets. These membranes are fabricatedby sandwiching a reinforcing fabric between two extruded thermoplasticsheets to provide a laminated structure. The thermoplastic extrudedsheets, which can be the same or different, often includeethylene-propylene reactor copolymers (e.g. CA10A available fromLyondellbasell), together with various additives, such as inert filler,anti-weathering additives, and flame retardants. As the skilled personappreciates, the type and amount of additives employed, such as thefiller, can impact the mechanical properties of the membrane includingtensile and tear strength.

While industry standards for thermoplastic roofing membranes aredesigned with an eye toward mechanically-attached thermoplastic roofingsystems, fully-adhered systems also exist. In fact, fully-adheredsystems are often viewed as superior roof systems. As the skilled personappreciates, a fully-adhered system is installed by using an adhesivethat attaches the membrane to the roof surface, where the adhesivesubstantially contacts all of the membrane surface adjacent to the roofdeck. In practice, liquid bond adhesives or pressure-sensitive adhesivesthat are factory applied to the membrane are often used.

A problem encountered when installing fully-adhered thermoplasticroofing sheets relates to the stiffness of the roofing sheet. As theskilled person appreciates, the integrity of a fully-adhered system canhinge on the degree to which the overall surface of the membrane isadhered. Where areas or pockets exist that are not adhered, the systemcan fail wind uplift tests. This is particularly true where the membraneis not fully adhered over uneven surfaces in the roof, such as fasteningplates that are often used to secure underlying insulation boards. Theskilled person understands that the stiffness of the sheet createsproblems when attempting to evenly apply the sheet over the roofsurface, especially uneven substrates. A goal often sought is theability to view the underlying contours of the roof surface though themembrane, which is indicative of complete adhesion to the roof. Wherethe membrane is too stiff, the membrane will not contour to theunderlying surface. A term often used in the art is telegraphing, whichrefers to the ability of the sheet to contour to the substrate andthereby allow the presence of the substrate to be noticed with the sheetin place.

Roofing membranes prepared from propylene-based copolymers are known.For example, U.S. Publ. No. 2010/0197844 teaches non-reinforced TPOmembranes, wherein the TPO may be prepared according to U.S. Pat. No.6,927,258, which discloses polymeric blends including a first polymerhaving a melt temperature above 110° C. and a heat of fusion of at least75 J/g, and a second polymer having a melting point of less than 105° C.and a heat of fusion of less than 75 J/g. Similar propylene-basedelastomers are disclosed in U.S. Publ. No. 2004/0198912, which disclosesmembranes, such as roof sheeting, formed from a blend of a first polymerhaving a melting point from 25° C. to 70° C., and a heat of fusion from2 J/g to 25 J/g, a second polymer having a melting point greater than130° C. and heat of fusion of greater than 80 J/g, from 1 to 40% byweight inorganic filler, and from 1 to 25% by weight processing oil.

SUMMARY OF THE INVENTION

One or more embodiments of the present invention provide a roof systemcomprising a substrate and thermoplastic membrane adhered to thesubstrate, where the thermoplastic membrane is characterized, prior tobeing adhered to the substrate, by a stiffness represented by a flexuralmodulus of less than 90 MPa, or by a Taber stiffness of less than 15, orby a Shore D hardness of less than 40, or by a combination of a flexuralmodulus of less than 90 MPa, a Taber stiffness of less than 15, and aShore D hardness of less than 40.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a single-extrudate membrane according toembodiments of the present invention.

FIG. 2 is a perspective view of a laminate membrane according toembodiments of the present invention.

FIG. 3 is a perspective view of laminate membrane according toembodiments of the present invention.

FIG. 4 is a cross-sectional view of a fully-adhered roofing systemaccording to embodiments of the present invention.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

Embodiments of the present invention are based, at least in part, on thediscovery of thermoplastic roofing membranes that can advantageously beused for fully-adhered roofing systems. These membranes arecharacterized by a relatively low stiffness (as may be indicated by lowflexural modulus), which allows the membranes to be installed usingfully-adhered attachment techniques while overcoming installationproblems associated with stiffness. While the relatively low stiffnesscarries with it a corresponding loss in certain mechanical properties,it has unexpectedly been discovered that the overall balance ofproperties is sufficient to provide technologically useful fully-adheredsystems. For example, while low stiffness may be associated with acorresponding loss in fastener pull-through strength or resistance, thefact that the membrane systems are fully adhered diminishes thedeleterious impact caused by this loss in property. Accordingly,embodiments of the invention are directed toward fully-adhered roofsystems that include membranes having relatively low stiffness asdescribed herein.

Membrane Construction

Membranes according to one or more embodiments of the present inventioncan be described with reference to FIG. 1. In this embodiment, themembrane includes planar body 11, which also may be referred to as sheet11 or panel 11. In this embodiment, panel 11 is a planar body thatconsists of a single extrudate. In one or more embodiments, planar body11 may be compositionally homogeneous or, in other embodiments, planarbody 11 may include one or more compositionally distinct layers 13 and15. For example, compositionally distinct layers 13 and 15 may be formedthrough coextrusion techniques, and reference may therefore be made tocoextruded layers 13 and 15, or first coextruded layer 13 and secondcoextruded layer 15.

In other embodiments, the membranes of one or more embodiments of thepresent invention may include two or more laminated layers. For example,as shown in FIG. 2, membrane 21 may include first layer 23 and secondlayer 25, which are laminated to one another, optionally with areinforcing scrim 27 disposed between laminated layers 23 and 25. Firstlayer 23 and second layer 25 may be compositionally similar with respectto one another. Or, in other embodiments, the layers may becompositionally distinct. Additionally, layers 23 and 25 may, withinthemselves, be compositionally homogeneous or, in other embodiments,they may be nonhomogeneous. For example, either first layer 23, secondlayer 25, or both layers 23 and 25, may include compositionally distinctcoextruded layers. In this respect, U.S. Publ. Nos. 2009/0137168,2009/0181216, 2009/0269565, 2007/0193167, and 2007/0194482 areincorporated herein by reference. As shown in FIG. 3, first layer 23 mayinclude compositionally distinct coextruded layers 31 and 33, and secondlayer 25 may include compositionally distinct coextruded layers 35 and37.

As will be discussed in greater detail below, one or more layers of themembranes of this invention include a propylene-based elastomer. Withreference to FIG. 3, these one or more layers may include upper middlelayer 33, as well as lower middle layer 35 and bottom layer 37. In theseor other embodiments, top layer 31 may also include the propylene-basedelastomer. In certain embodiments, top layer 31 includes apropylene-based polymer that is distinct from a propylene-basedelastomer, such as a propylene-based olefinic polymer as will bedescribed in greater detail below. In these or other embodiments, toplayer 31 is devoid of a propylene-based elastomer. Additionally, incertain embodiments, bottom layer 37 may include a functionalizedthermoplastic resin. In one or more embodiments, top layer 31 includesflame retardants and other weathering additives that may providesufficient environmental protection to the polymers, while at least oneof layers 33, 35, and 37 may include fillers such as mineral fillers.

Membrane Characteristics

As discussed above, the membranes employed in the practice of thisinvention are advantageously characterized by a relatively lowstiffness. In one or more embodiments, the low stiffness may berepresented by a relatively low flexural modulus, as determined by ASTMD790. In other words, relatively low flexural modulus is indicative oflow stiffness. For example, the membranes of one or more embodiments ofthis invention may have a flexural modulus, according to ASTM D790, ofless than 90 MPa, in other embodiments less than 80 MPa, in otherembodiments less than 70 MPa, in other embodiments less than 60 MPa, inother embodiments less than 50 MPa, in other embodiments less than 40MPa, and in other embodiments less than 30 MPa. In these or otherembodiments, the membranes may be characterized by a flexural modulus offrom about 5 to about 90 MPa, in other embodiments from about 10 toabout 80 MPa, and in other embodiments from about 20 to about 70 MPa.

In these or other embodiments, the relatively low stiffness of themembranes of this invention may be represented by a relatively low Shorehardness (e.g. low Shore A or Shore D). For example, the membranes maybe characterized by a Shore D hardness, as determined by ASTM D2240, ofless than 40, in other embodiments less than 30, and in otherembodiments less than 20. In these or other embodiments, the membranesmay be characterized by a hardness of from about 70 Shore A to about 40Shore D, in other embodiments from about 80 Shore A to about 30 Shore D,and in other embodiments from about 90 Shore A to about 20 Shore D.

In these or other embodiments, the relatively low stiffness of themembranes of this invention may be represented by a relatively low Taberstiffness. As the skilled person appreciates, Taber stiffness is anadvantageous measurement for reinforced membrane materials because themeasurements can be taken on samples that include a fabricreinforcement. The skilled person understands that these Taber stiffnessvalues can be obtained by employing a Taber stiffness tester, such as amodel 510-E Taber V-5 stiffness tester. The skilled person understandsthat the results of the Taber stiffness test are reported in stiffnessunits with lower values representing membranes of lower stiffness. Inone or more embodiments, the membranes employed in practice of thepresent invention may be characterized by a Taber stiffness of less than15, in other embodiments less than 12, in other embodiments less than 8,in other embodiments less than 6, and in other embodiments less than 4.In these or other embodiments, the membranes may be characterized by astiffness of from about 1 to about 15, in other embodiments from about 2to about 10, and in other embodiments from about 3 to about 6. In one ormore embodiments, the Taber stiffness values of the membranes of thepresent invention are at least 100%, in other embodiments at least 120%,and in other embodiments at least 150% lower than comparative membranesprepared using propylene-based thermoplastic polyolefins such as reactorcopolymers as described herein

Membrane Composition Propylene-Based Elastomer

In one or more embodiments, the advantageously low stiffness isattributable to the polymeric composition of one or more layers of themembrane. In one or more embodiments, the polymeric composition of oneor more layers includes a propylene-based elastomer. In these or otherembodiments, the polymeric composition includes a blend of apropylene-based elastomer and a propylene-based thermoplastic resin. Inone or more embodiments, both propylene-based elastomer and thepropylene-based thermoplastic resin have isotactic propylene sequenceslong enough to crystallize. In this regard, U.S. Pat. No. 6,927,258, andU.S. Publ. Nos. 2004/0198912 and 2010/0197844 are incorporated herein byreference.

In one or more embodiments, the propylene-based elastomer ispropylene/alpha-olefin copolymer with semi-crystalline isotacticpropylene segments. The alpha-olefin content (e.g. polymerized ethylenecontent) may range from about 5 to about 18%, or in other embodimentsfrom about 10 to about 15%.

In one or more embodiments, the propylene-based elastomer ischaracterized by a melting point that is less than 110° C. and a heat offusion of less than 75 J/g.

In one embodiment, the propylene based elastomers of the presentinvention have a glass transition temperature (Tg) in the range of about−25 to −35° C. The Tg as used herein is the temperature above which apolymer becomes soft and pliable, and below which it becomes hard andglassy. The propylene-based elastomers may have a MFR range measured at230° C. of between about 0.5 to about 25, and a melt temperature rangeof about 50 to 120° C.

In one embodiment, the propylene-based elastomers of the presentinvention have a shore A hardness range of about 60 to about 90.

In those embodiments where the propylene-based elastomer is blended witha propylene-based thermoplastic resin, the propylene-based thermoplasticresin may include a crystalline resin. In particular embodiments, thepropylene-based thermoplastic resin is characterized by a melting pointthat is greater than 110° C. and a heat of fusion greater than 75 J/g.In one or more embodiments, the propylene-based thermoplastic resin isstereoregular polypropylene. In one or more embodiments, the weightratio of the propylene-based elastomer to the thermoplastic resin withinthe blend may vary in the range of 1:99 to 95:5 by weight and, inparticular, in the range 2:98 to 70:30 by weight.

In one embodiment, the propylene-based elastomers of the presentinvention have a flexural modulus range of about 500 to about 6000 Psi,or in other embodiments about 1500 to about 5000 psi.

Filler

In one or more embodiments, one or more layers of the membranes employedin practicing the present invention may include one or more fillermaterials including, but not limited to, mineral fillers. In one or moreembodiments, these fillers may include inorganic materials that may aidin reinforcement, heat aging resistance, green strength performance,and/or flame resistance. In other embodiments, these materials aregenerally inert with respect to the composition and therefore simply actas diluent to the polymeric constituents. In one or more embodiments,mineral fillers include clays, silicates, titanium dioxide, talc(magnesium silicate), mica (mixtures of sodium and potassium aluminumsilicate), alumina trihydrate, antimony trioxide, calcium carbonate,titanium dioxide, silica, magnesium hydroxide, calcium borate ore, andmixtures thereof.

Suitable clays may include airfloated clays, water-washed clays,calcined clays, surface-treated clays, chemically-modified clays, andmixtures thereof.

Suitable silicates may include synthetic amorphous calcium silicates,precipitated, amorphous sodium aluminosilicates, and mixtures thereof.

Suitable silica (silicon dioxide) may include wet-processed, hydratedsilicas, crystalline silicas, and amorphous silicas (noncrystalline).

In one or more embodiments, the fillers are not surface modified orsurface functionalized.

In one or more embodiments, the mineral fillers are characterized by anaverage particle size of at least 1 μm, in other embodiments at least 2μm, in other embodiments at least 3 μm, in other embodiments at least 4μm, and in other embodiments at least 5 μm. In these or otherembodiments, the mineral fillers are characterized by an averageparticle size of less than 15 μm, in other embodiments less than 12 μm,in other embodiments less than 10 μm, and in other embodiments less than8 μm. In these or other embodiments, the mineral filler has an averageparticle size of between 1 and 15 μm, in other embodiments between 3 and12 μm, and in other embodiments between 6 and 10 μm.

Other Ingredients

One or more layers of the thermoplastic membranes employed in thepractice of this invention may also include other ingredients such asthose that are conventional in thermoplastic membranes. For example,other useful additives or constituents may include flame retardants,stabilizers, pigments, and fillers.

In one or more embodiments, useful flame retardants include and compoundthat will increase the burn resistivity, particularly flame spread suchas tested by UL 94 and/or UL 790, of the laminates of the presentinvention. Useful flame retardants include those that operate by forminga char-layer across the surface of a specimen when exposed to a flame.Other flame retardants include those that operate by releasing waterupon thermal decomposition of the flame retardant compound. Useful flameretardants may also be categorized as halogenated flame retardants ornon-halogenated flame retardants.

Exemplary non-halogenated flame retardants include magnesium hydroxide,aluminum trihydrate, zinc borate, ammonium polyphosphate, melaminepolyphosphate, and antimony oxide (Sb₂O₃). Magnesium hydroxide (Mg(OH)₂)is commercially available under the tradename Vertex™ 60, ammoniumpolyphosphate is commercially available under the tradename Exolite™ AP760 (Clarian), which is sold together as a polyol masterbatch, melaminepolyphosphate is available under the tradename Budit™ 3141 (Budenheim),and antimony oxide (Sb₂O₃) is commercially available under the tradenameFireshield™. Those flame retardants from the foregoing list that arebelieved to operate by forming a char layer include ammoniumpolyphosphate and melamine polyphosphate.

In one or more embodiments, treated or functionalized magnesiumhydroxide may be employed. For example, magnesium oxide treated with orreacted with a carboxylic acid or anhydride may be employed. In oneembodiment, the magnesium hydroxide may be treated or reacted withstearic acid. In other embodiments, the magnesium hydroxide may betreated with or reacted with certain silicon-containing compounds. Thesilicon-containing compounds may include silanes, polysiloxanesincluding silane reactive groups. In other embodiments, the magnesiumhydroxide may be treated with maleic anhydride. Treated magnesiumhydroxide is commercially available. For example, Zerogen™ 50.

Examples of halogenated flame retardants may include halogenated organicspecies or hydrocarbons such as hexabromocyclododecane orN,N′-ethylene-bis-(tetrabromophthalimide). Hexabromocyclododecane iscommercially available under the tradename CD-75P™ (ChemTura).N,N′-ethylene-bis-(tetrabromophthalimide) is commercially availableunder the tradename Saytex™ BT-93 (Albemarle).

In one or more embodiments, the use of char-forming flame retardants(e.g. ammonium polyphosphate and melamine polyphosphate) hasunexpectedly shown advantageous results when used in conjunction withnanoclay within the cap layer of the laminates of the present invention.It is believed that there may be a synergistic effect when thesecompounds are present in the cap layer. As a result, the cap layer ofthe laminates of the certain embodiments of the present invention aredevoid of or substantially devoid of halogenated flame retardants and/orflame retardants that release water upon thermal decomposition.Substantially devoid referring to that amount or less that does not havean appreciable impact on the laminates, the cap layer, and/or the burnresistivity of the laminates.

In one or more embodiments, one or more layers of the membranes employedin this invention may include stabilizers. Stabilizers may include oneor more of a UV stabilizer, an antioxidant, and an antiozonant. UVstabilizers include Tinuvin™ 622. Antioxidants include Irganox™ 1010.

In one or more embodiments, one or more layers of the membranes of thepresent invention may include expandable graphite, which may also bereferred to as expandable flake graphite, intumescent flake graphite, orexpandable flake. Generally, expandable graphite includes intercalatedgraphite in which an intercallant material is included between thegraphite layers of graphite crystal or particle. Examples ofintercallant materials include halogens, alkali metals, sulfates,nitrates, various organic acids, aluminum chlorides, ferric chlorides,other metal halides, arsenic sulfides, and thallium sulfides. In certainembodiments of the present invention, the expandable graphite includesnon-halogenated intercallant materials. In certain embodiments, theexpandable graphite includes sulfate intercallants, also referred to asgraphite bisulfate. As is known in the art, bisulfate intercalation isachieved by treating highly crystalline natural flake graphite with amixture of sulfuric acid and other oxidizing agents which act tocatalyze the sulfate intercalation. Expandable graphite useful in theapplications of the present invention are generally known as describedin International Publ. No. WO/2014/078760, which is incorporated hereinby reference.

Commercially available examples of expandable graphite include HPMSExpandable Graphite (HP Materials Solutions, Inc., Woodland Hills,Calif.) and Expandable Graphite Grades 1721 (Asbury Carbons, Asbury,N.J.). Other commercial grades contemplated as useful in the presentinvention include 1722, 3393, 3577, 3626, and 1722HT (Asbury Carbons,Asbury, N.J.).

In one or more embodiments, the expandable graphite may be characterizedas having a mean or average size in the range from about 30 μm to about1.5 mm, in other embodiments from about 50 μm to about 1.0 mm, and inother embodiments from about 180 to about 850 μm. In certainembodiments, the expandable graphite may be characterized as having amean or average size of at least 30 μm, in other embodiments at least 44μm, in other embodiments at least 180 μm, and in other embodiments atleast 300 μm. In one or more embodiments, expandable graphite may becharacterized as having a mean or average size of at most 1.5 mm, inother embodiments at most 1.0 mm, in other embodiments at most 850 μm,in other embodiments at most 600 μm, in yet other embodiments at most500 μm, and in still other embodiments at most 400 μm. Useful expandablegraphite includes Graphite Grade #1721 (Asbury Carbons), which has anominal size of greater than 300 μm.

In one or more embodiments of the present invention, the expandablegraphite may be characterized as having a nominal particle size of 20×50(US sieve). US sieve 20 has an opening equivalent to 0.841 mm and USsieve 50 has an opening equivalent to 0.297 mm. Therefore, a nominalparticle size of 20×50 indicates the graphite particles are at least0.297 mm and at most 0.841 mm.

In one or more embodiments, the expandable graphite may be characterizedby an onset temperature ranging from about 100° C. to about 250° C.; inother embodiments from about 160° C. to about 225° C.; and in otherembodiments from about 180° C. to about 200° C. In one or moreembodiments, the expandable graphite may be characterized by an onsettemperature of at least 100° C., in other embodiments at least 130° C.,in other embodiments at least 160° C., and in other embodiments at least180° C. In one or more embodiments, the expandable graphite may becharacterized by an onset temperature of at most 250° C., in otherembodiments at most 225° C., and in other embodiments at most 200° C.Onset temperature may also be interchangeably referred to as expansiontemperature; and may also be referred to as the temperature at whichexpansion of the graphite starts.

In one or more embodiments, one or more layers of the membranes of thepresent invention include a nanoclay. Nanoclays include the smectiteclays, which may also be referred to as layered silicate minerals.Useful clays are generally known as described in U.S. Pat. No. 6,414,070and U.S. Pat. Publ. No. 2009/0269565, which are incorporated herein byreference. In one or more embodiments, these clays include exchangeablecations that can be treated with organic swelling agents such as organicammonium ions, to intercalate the organic molecules between adjacentplanar silicate layers, thereby substantially increasing the interlayerspacing. The expansion of the interlayer distance of the layeredsilicate can facilitate the intercalation of the clay with othermaterials. The interlayer spacing of the silicates can be furtherincreased by formation of the polymerized monomer chains between thesilicate layers. The intercalated silicate platelets act as a nanoscale(sub-micron size) filler for the polymer.

Intercalation of the silicate layers in the clay can take place eitherby cation exchange or by absorption. For intercalation by absorption,dipolar functional organic molecules such as nitrile, carboxylic acid,hydroxy, and pyrrolidone groups are desirably present on the claysurface. Intercalation by absorption can take place when either acid ornon-acid clays are used as the starting material. Cation exchange cantake place if an ionic clay containing ions such as, for example, Na⁺,K⁺, Ca⁺⁺, Ba⁺⁺, and Li⁺ is used. Ionic clays can also absorb dipolarorganic molecules.

Smectite clays include, for example, montmorillonite, saponite,beidellite, hectorite, and stevensite. In one or more embodiments, thespace between silicate layers may be from about 15 to about 40×, and inother embodiments from about 17 to about 36×, as measured by small angleX-ray scattering. Typically, a clay with exchangeable cations such assodium, calcium and lithium ions may be used. Montmorillonite in thesodium exchanged form is employed in one or more embodiments.

Organic swelling agents that can be used to treat the clay includequaternary ammonium compound, excluding pyridinium ion, such as, forexample, poly(propylene glycol)bis(2-aminopropyl ether),poly(vinylpyrrolidone), dodecylamine hydrochloride, octadecylaminehydrochloride, and dodecylpyrrolidone. These treated clays arecommercially available. One or more of these swelling agents can beused.

Functionalized Polymers

In one or more embodiments, one or more layers of the membranes employedin practice of this invention includes a functionalized polymer. In oneor more embodiments, the functionalized polymer is a thermoplasticpolymer that includes at least one functional group. The functionalgroup, which may also be referred to as a functional substituent orfunctional moiety, includes a hetero atom. In one or more embodiments,the functional group includes a polar group. Examples of polar groupsinclude hydroxy, carbonyl, ether, ester halide, amine, imine, nitrile,oxirane (e.g., epoxy ring) or isocyanate groups. Exemplary groupscontaining a carbonyl moiety include carboxylic acid, anhydride, ketone,acid halide, ester, amide, or imide groups, and derivatives thereof. Inone embodiment, the functional group includes a succinic anhydridegroup, or the corresponding acid, which may derive from a reaction(e.g., polymerization or grafting reaction) with maleic anhydride, or aβ-alkyl substituted propanoic acid group or derivative thereof. In oneor more embodiments, the functional group is pendant to the backbone ofthe hydrocarbon polymer. In these or other embodiments, the functionalgroup may include an ester group. In specific embodiments, the estergroup is a glycidyl group, which is an ester of glycidol and acarboxylic acid. A specific example is a glycidyl methacrylate group.

In one or more embodiments, the functionalized thermoplastic polymer maybe prepared by grafting a graft monomer to a thermoplastic polymer. Theprocess of grafting may include combining, contacting, or reacting athermoplastic polymer with a graft monomer. These functionalizedthermoplastic polymers include those described in U.S. Pat. Nos.4,957,968, 5,624,999, and 6,503,984, which are incorporated herein byreference.

The thermoplastic polymer that can be grafted with the graft monomer mayinclude solid, generally high molecular weight plastic materials. Theseplastics include crystalline and semi-crystalline polymers. In one ormore embodiments, these thermoplastic polymers may be characterized by acrystallinity of at least 20%, in other embodiments at least 25%, and inother embodiments at least 30%. Crystallinity may be determined bydividing the heat of fusion of a sample by the heat of fusion of a 100%crystalline polymer, which is assumed to be 209 joules/gram forpolypropylene or 350 joules/gram for polyethylene. Heat of fusion can bedetermined by differential scanning calorimetry. In these or otherembodiments, the thermoplastic polymers to be functionalized may becharacterized by having a heat of fusion of at least 40 J/g, in otherembodiments in excess of 50 J/g, in other embodiments in excess of 75J/g, in other embodiments in excess of 95 J/g, and in other embodimentsin excess of 100 J/g.

In one or more embodiments, the thermoplastic polymers, prior tografting, may be characterized by a weight average molecular weight(M_(w)) of from about 100 kg/mole to about 2,000 kg/mole, and in otherembodiments from about 300 kg/mole to about 600 kg/mole. They may alsocharacterized by a number-average molecular weight (M_(n)) of about 80kg/mole to about 800 kg/mole, and in other embodiments about 90 kg/moleto about 200 kg/mole. Molecular weight may be determined by sizeexclusion chromatography (SEC) by using a Waters 150 gel permeationchromatograph equipped with the differential refractive index detectorand calibrated using polystyrene standards.

In one or more embodiments, these thermoplastic polymer, prior tografting, may be characterized by a melt flow of from about 0.3 to about2,000 dg/min, in other embodiments from about 0.5 to about 1,000 dg/min,and in other embodiments from about 1 to about 1,000 dg/min, per ASTMD-1238 at 230° C. and 2.16 kg load.

In one or more embodiments, these thermoplastic resins, prior tografting, may have a melt temperature (T_(m)) that is from about 110° C.to about 250° C., in other embodiments from about 120 to about 170° C.,and in other embodiments from about 130° C. to about 165° C. In one ormore embodiments, they may have a crystallization temperature (T_(c)) ofthese optionally at least about 75° C., in other embodiments at leastabout 95° C., in other embodiments at least about 100° C., and in otherembodiments at least 105° C., with one embodiment ranging from 105° to115° C.

Exemplary thermoplastic polymers that may be grafted includepolyolefins, polyolefin copolymers, and non-olefin thermoplasticpolymers. Polyolefins may include those thermoplastic polymers that areformed by polymerizing ethylene or α-olefins such as propylene,1-butene, 1-hexene, 1-octene, 2-methyl-1-propene, 3-methyl-1-pentene,4-methyl-1-pentene, 5-methyl-1-hexene, and mixtures thereof. Copolymersof ethylene and propylene and ethylene and/or propylene with anotherα-olefin such as 1-butene, 1-hexene, 1-octene, 2-methyl-1-propene,3-methyl-1-pentene, 4-methyl-1-pentene, 5-methyl-1-hexene or mixturesthereof is also contemplated. Other polyolefin copolymers may includecopolymers of olefins with styrene such as styrene-ethylene copolymer orpolymers of olefins with α,β-unsaturated acids, α,β-unsaturated esterssuch as polyethylene-acrylate copolymers. Non-olefin thermoplasticpolymers may include polymers and copolymers of styrene, α,β-unsaturatedacids, α,β-unsaturated esters, and mixtures thereof. For example,polystyrene, polyacrylate, and polymethacrylate may be functionalized.

These homopolymers and copolymers may be synthesized by using anappropriate polymerization technique known in the art. These techniquesmay include conventional Ziegler-Natta, type polymerizations, catalysisemploying single-site organometallic catalysts including, but notlimited to, metallocene catalysts, and high-pressure free radicalpolymerizations.

The degree of functionalization of the functionalized thermoplasticpolymer may be recited in terms of the weight percent of the pendentfunctional moiety based on the total weight of the functionalizedpolymer. In one or more embodiments, the functionalized thermoplasticpolymer may include at least 0.2% by weight, in other embodiments atleast 0.4% by weight, in other embodiments at least 0.6% by weight, andin other embodiments at least 1.0 weight percent functionalization, inthese or other embodiments, the functionalized thermoplastic polymersmay include less than 10% by weight, in other embodiments less than 5%by weight, in other embodiments less than 3% by weight, and in otherembodiments less than 2% by weight functionalization.

In one or more embodiments, where the functionalized thermoplasticpolymer is a functionalized propylene-based polymer, it can becharacterized by a melt flow rate of from about 20 to about 2,000dg/min, in other embodiments from about 100 to about 1,500 dg/min, andin other embodiments from about 150 to about 750 dg/min, per ASTM D-1238at 230° C. and 2.16 kg load. In one or more embodiments, where thefunctionalized thermoplastic polymer is a functionalized ethylene-basedpolymer, it can be characterized by a melt flow index of from about 0.2to about 2,000 dg/min, in other embodiments from about 1 to about 1,000dg/min, and in other embodiments from about 5 to about 100 dg/min, perASTM D-1238 at 190° C. and 2.16 kg load.

Functionalized thermoplastic polymers are commercially available. Forexample, maleated propylene-based polymers may be obtained under thetradename FUSABOND™ (DuPont), POLYBOND™ (Crompton), and EXXELOR™(ExxonMobil). Another examples includes polymers or oligomers includingone or more glycidyl methacrylate groups such as Lotader™ AX8950(Arkema).

Conventional Thermoplastic Resin

In one or more embodiments, one or more layers of the membranes employedin the present invention may include a conventional thermoplastic resin.In one or more embodiments, a conventional thermoplastic resin may bedistinguished from the propylene-based elastomer based upon melttemperature and heat of fusion. In one or more embodiments, theconventional thermoplastic resin may have a heat of fusion that isgreater than 75 J/g, in other embodiments greater than 80 J/g, and inother embodiments greater than 85 J/g. In these or other embodiments,the conventional thermoplastic resin may have a melt temperature that isgreater than 105° C., in other embodiments greater than 110° C., and inother embodiments greater than 115° C.

In one or more embodiments, the conventional thermoplastic polymer mayinclude an olefinic reactor copolymer, which may also be referred to asin-reactor copolymer. Reactor copolymers are generally known in the artand may include blends of olefinic polymers that result from thepolymerization of ethylene and α-olefins (e.g., propylene) with sundrycatalyst systems. In one or more embodiments, these blends are made byin-reactor sequential polymerization. Reactor copolymers useful in oneor more embodiments include those disclosed in U.S. Pat. No. 6,451,897,which is incorporated therein by reference. Reactor copolymers, whichare also referred to as TPO resins, are commercially available under thetradename HIFAX™ (Lyondellbassel); these materials are believed toinclude in-reactor blends of ethylene-propylene rubber and polypropyleneor polypropylene copolymers. Other useful thermoplastic olefins includethose available under the tradename T00G-00 (Ineos). In one or moreembodiments, the in-reactor copolymers may be physically blended withother polyolefins. For example, in reactor copolymers may be blendedwith linear low density polyethene.

Amounts Filler

In one or more embodiments, the one or more layers of the membranesemployed in the present invention include at least 10 weight percent, inother embodiments at least 15 weight percent, in other embodiments atleast 20 weight percent, in other embodiments at least 25 weightpercent, in other embodiments at least 30 weight percent, 33 weightpercent, in other embodiments at least 40 weight percent, and in otherembodiments at least 45 weight percent of the filler (e.g. mineralfiller) based on the entire weight of the given layer of the membranethat includes the filler. In one or more embodiments, one or more layersof the membranes of the present invention include at most 80 weightpercent, in other embodiments at most 70 weight percent, and in otherembodiments at most 60 weight percent of the filler based on the entireweight of the given layer of the membrane that includes the filler. Inone or more embodiments, one or more layers of the membranes of thepresent invention include from about 33 to about 80, in otherembodiments from about 40 to about 70, and in other embodiments fromabout 45 to about 60 weight percent of the filler based upon the entireweight of the given layer of the membrane that includes the filler.

Functionalized Polymer

In one or more embodiments, the one or more layers of the membranes ofthe present invention that include the functionalized polymer include atleast 1 weight percent, in other embodiments at least 2 weight percent,in other embodiments at least 3 weight percent, in other embodiments atleast 5 weight percent, and in other embodiments at least 7 weightpercent of the functionalized polymer (e.g. hydroxyl-bearing polymer)based on the entire weight of the given layer of the membrane thatincludes the functionalized polymer. In one or more embodiments, the oneor more layers of the membranes of the present invention that includethe functionalized polymer include at most 50 weight percent, in otherembodiments at most 25 weight percent, and in other embodiments at most15 weight percent of the functionalized polymer based on the entireweight of the given layer of the membrane that includes thefunctionalized polymer. In one or more embodiments, the one or morelayers of the membranes of the present invention that include thefunctionalized polymer include from about 3 to about 50, in otherembodiments from about 5 to about 25, and in other embodiments fromabout 7 to about 15 weight percent of the functionalized polymer basedupon the entire weight of the given layer of the membrane that includesthe functionalized polymer.

Specific Embodiments

Specific embodiments of the membranes employed in the practice of thepresent invention can be described with reference to FIG. 3. In one ormore embodiments, the membranes employed in the present invention mayinclude propylene-based elastomer in upper-middle layer 33, lower-middlelayer 35, optionally top layer 31, and optionally bottom layer 37. Inparticular embodiments, while upper-middle layer 33 and lower middlelayer 35 may include propylene-based elastomer, top layer 31 includesconventional thermoplastic polymer. In particular embodiments, thepolymeric component of top layer 31 includes at least 90%, in otherembodiments at least 95%, and in other embodiments at least 99%conventional thermoplastic polymer.

In one or more embodiments, bottom layer 37 includes functionalizedthermoplastic polymer. In one or more embodiments, bottom layer 37includes from about 1 to about 10, in other embodiments from about 3 toabout 8, and in other embodiments from about 4 to about 6% by weightfunctionalized thermoplastic polymer, based upon the entire weight ofthe layer.

In one or more particular embodiments, top layer 31, upper-middle layer33, lower-middle layer 35, and bottom layer 37 may include distinctamounts of one or more distinct or similar fillers. For example, in oneor more embodiments, top layer 31 may include from about 15 to about 50,in other embodiments from about 20 to about 40, and in other embodimentsfrom about 25 to about 35% by weight magnesium hydroxide filler, basedon the entire weight of the layer, while upper-middle layer 33,lower-middle layer 35, and bottom layer 37 include less than 20, inother embodiments less than 10, and in other embodiments less than 5% byweight magnesium hydroxide filler, based upon the entire weight of therespective layers.

In one or more particular embodiments, at least one of upper-middlelayer 33, lower-middle layer 35, and bottom layer 37 individuallyinclude, or in certain embodiments each of layers 33, 35, and 37include, from about 25 to about 75, in other embodiments from about 35to about 65, and in other embodiments from about 45 to about 65% byweight calcium carbonate filler, based on the entire weight of thelayer.

Method of Making

In one or more embodiments, the membranes employed in the presentinvention may be prepared by employing conventional techniques. Forexample, the various ingredients can be separately fed into an extruderand extruded into membrane and, optionally, laminated into a laminatesheet. In other embodiments, the various ingredients can be combined andmixed within a mixing apparatus such as an internal mixer and thensubsequently fabricated into membrane sheets or laminates.

In one or more embodiments, the membranes of the present invention maybe prepared by extruding a polymeric composition into a sheet. Multiplesheets may be extruded and joined to form a laminate. A membraneincluding a reinforcing layer may be prepared by extruding at least onesheet on and/or below a reinforcement (e.g., a scrim). In otherembodiments, the polymeric layer may be prepared as separate sheets, andthe sheets may then be calandered with the scrim sandwiched therebetween to form a laminate. In one or more embodiments, the membranes ofthe present invention are prepared by employing co-extrusion technology.Useful techniques include those described in co-pending U.S. Ser. Nos.11/708,898 and 11/708,903, which are incorporated herein by reference.

Following extrusion, and after optionally joining one or more polymericlayers, or optionally joining one or more polymeric layer together witha reinforcement, the membrane may be fabricated to a desired thickness.This may be accomplished by passing the membrane through a set ofsqueeze rolls positioned at a desired thickness. The membrane may thenbe allowed to cool and/or rolled for shipment and/or storage.

The polymeric composition that may be extruded to form the polymericsheet may include the ingredients or constituents described herein. Forexample, the polymeric composition may include propylene-basedelastomer, filler, and functionalized polymers defined herein. Theingredients may be mixed together by employing conventional polymermixing equipment and techniques. In one or more embodiments, an extrudermay be employed to mix the ingredients. For example, single-screw ortwin-screw extruders may be employed.

Fully-Adhered Roofing System

The fully-adhered roofing systems of the present invention can bedescribed with reference to FIG. 4. Roofing system 40 includes a roofdeck 51, optional insulation layer 53, optional protection layer 55,optional existing membrane 57, adhesive layer 60, and membrane 71, wheremembrane 71 is a membrane according to one or more embodiments of thepresent invention. For purposes of this specification, the material towhich the adhesive secures the membrane, which is the uppermost layer,can be referred to as the substrate. For example, where the membrane isadhesively secured to an insulation board or layer, the insulation boardor layer may be referred to as a substrate.

Practice of this invention is not limited by the selection of anyparticular roof deck. Accordingly, the roofing systems herein caninclude a variety of roof decks. Exemplary roof decks include concretepads, steel decks, wood beams, and foamed concrete decks.

In one or more embodiments, the existing membranes may include curedrubber systems such as EPDM membranes, thermoplastic polymers systemssuch as TPO membranes, or asphalt-based systems such as modified asphaltmembranes and/or built roof systems.

Practice of this invention is likewise not limited by the selection ofany particular insulation board. Moreover, the insulation boards areoptional. Several insulation materials can be employed includingpolyurethane or polyisocyanurate cellular materials. These boards areknown as described in U.S. Pat. Nos. 6,117,375, 6,044,604, 5,891,563,5,573,092, U.S. Publication Nos. 2004/0109983, 2003/0082365,2003/0153656, 2003/0032351, and 2002/0013379, as well as U.S. Ser. Nos.10/640,895, 10/925,654, and 10/632,343, which are incorporated herein byreference. As those skilled in the art appreciate, insulation boards andcover boards may carry a variety of facer materials including, but notlimited to, paper facers, fiberglass-reinforced paper facers, fiberglassfacers, coated fiberglass facers, metal facers such as aluminum facers,and solid facers such as wood.

In one or more embodiments, cover boards may include high densitypolyurethane or polyisocyanurate board as disclosed in U.S. Publ. Nos.2006/0127664, 2013/0164524, 2014/0011008, 2013/0036694, and2012/0167510, which are incorporated herein by reference. In otherembodiments, the cover boards may include construction boards such asDensDeck.

In other embodiments, these membranes may be employed to cover flat orlow-slope roofs following a re-roofing event. In one or moreembodiments, the membranes may be employed for re-roofing as describedin U.S. Publication No. 2006/0179749, which are incorporated herein byreference.

Practice of the present invention is also not necessarily limited by theadhesive employed to bond the membrane to the substrate. For example,the adhesive may include an adhesive that forms a bond through curingaction such as is the case with a liquid bond adhesive (e.g. a butylrubber adhesive) or a polyurethane adhesive. In other embodiments, theadhesive may be a pressure-sensitive adhesive, which may be applied tothe membrane at the location where the membrane is manufactured (e.g. afactory-applied pressure-sensitive adhesive).

As used within the specification, the term “fully-adhered roofingsystem” refers to a roofing system wherein the primary mode ofattachment of the membrane to the underlying substrate is through theuse of an adhesive. In one or more embodiments, this mode of attachmentincludes the situation where at least 50%, in other embodiments at least70%, in other embodiments at least 90%, and in other embodiments atleast 98% of the underlying surface of the membrane (i.e., thesubstrate-contacting planar surface of the membrane) is adhered to thesubstrate through an adhesive.

Various modifications and alterations that do not depart from the scopeand spirit of this invention will become apparent to those skilled inthe art. This invention is not to be duly limited to the illustrativeembodiments set forth herein.

What is claimed is:
 1. A roof system comprising: a substrate andthermoplastic membrane adhered to the substrate, where the thermoplasticmembrane is characterized, prior to being adhered to the substrate, by astiffness represented by a flexural modulus of less than 90 MPa, or by aTaber stiffness of less than 15, or by a Shore D hardness of less than40, or by a combination of a flexural modulus of less than 90 MPa, aTaber stiffness of less than 15, and a Shore D hardness of less than 40,where the membrane is a multi-layered membrane including a top layerlocated opposite the substrate and forming the outermost layer of themembrane, an upper-middle layer disposed between the top layer and afabric reinforcement, and a lower layer disposed between said fabricreinforcement and said substrate, where said upper-middle layer and saidlower layer include propylene-based elastomer, and where said top layeris devoid of propylene-based elastomer.
 2. The roof system of claim 1,where the substrate is selected from the group consisting of a roofdeck, an insulation board, a cover board, and an existing membrane. 3.The roof system of claim 1, where the thermoplastic membrane includesfirst and second opposed planar surface with one of the opposed planarsurfaces being adhered to the substrate.
 4. The roof system of claim 1,where at least 50% of the at least one planar surface of the membrane isadhered to the substrate.
 5. The roof system of claim 1, where themembrane is adhered to the substrate through a polyurethane adhesive. 6.The roof system of claim 1, where the membrane is adhered to thesubstrate through a pressure-sensitive adhesive.
 7. The roof system ofclaim 1, where the membrane includes one or more layers, and where atleast one layer includes a propylene-based elastomer.
 8. The roof systemof claim 1, where the membrane is characterized by a flexural modulus ofless than 90 MPa.
 9. The roof system of claim 1, where the membrane ischaracterized by a Taber stiffness of less than
 15. 10. The roof systemof claim 1, where the membrane is characterized by a Shore D hardness ofless than
 40. 11. The roof system of claim 1, where the membrane ischaracterized by a flexural modulus of less than 70 MPa.
 12. The roofsystem of claim 1, where the membrane is characterized by a Taberstiffness of less than
 8. 13. The roof system of claim 1, where themembrane is characterized by a Shore D hardness of less than
 20. 14. Theroof system of claim 1, where said top layer includes from about 15 toabout 50 weight percent magnesium hydroxide, and where said upper-middlelayer and said lower layer include less than 20 weight percent magnesiumhydroxide.
 15. The roof system of claim 1, where said upper-middle layerand said lower layer include from about 25 to about 75 weight percentcalcium carbonate.